"I’m gravely concerned about reports of an Israeli plan to proceed with a ground assault on Rafah," Ghebreyesus wrote on X, emphasizing that an escalation of violence in the densely populated area would lead to even more deaths and suffering, especially due to crowded health facilities.
"The 1.2 million people in Rafah do not have anywhere safe to move to," he added.
Highlighting the lack of a fully functional and secure health facility accessible to displaced individuals in Gaza, Ghebreyesus said that people are “too fragile, hungry, and sick” to move elsewhere.
"The humanitarian catastrophe must not be allowed to worsen," he added.
Israel has waged a deadly military offensive on the Gaza Strip since an Oct. 7 cross-border attack by Hamas in which 1,163 people were killed.
More than 31,500 Palestinians, mostly women and children, have since been killed in Gaza, and 73,546 others injured amid mass destruction and shortages of necessities.
The Israeli war has pushed 85% of Gaza’s population into internal displacement amid a crippling blockade of most food, clean water and medicine, while 60% of the enclave's infrastructure has been damaged or destroyed, according to the UN.